Nonaqueous electrolyte secondary battery

Abstract

A nonaqueous electrolyte secondary battery includes a flat winding electrode assembly including a positive electrode substrate exposed portion on one end and a negative electrode substrate exposed portion on the other end. The winding numbers of the positive and the negative electrode substrate exposed portions are each 30 or more. The positive and negative electrode substrate exposed portions each have an outermost surface welded and connected with a positive and a negative electrode collectors, respectively. A nonaqueous electrolyte used to fabricate the battery contains a lithium salt having an oxalate complex as an anion. At the welded connection portions, all of the layers of the positive electrode substrate exposed portion are melted to be welded and connected to the positive electrode collector, and all of the layers of the negative electrode substrate exposed portion are melted to be welded and connected to the negative electrode collector.

Description

TECHNICAL FIELD[0001]The present invention relates to a nonaqueous electrolyte secondary battery that has excellent cycling characteristics.BACKGROUND ART[0002]Alkaline secondary batteries typified by nickel-hydrogen batteries and nonaqueous electrolyte secondary batteries typified by lithium ion batteries have been widely used as a power supply for driving portable electronic equipment, such as cell phones including smartphones, portable personal computers, PDAs, and portable music players. In addition, alkaline secondary batteries and nonaqueous electrolyte secondary batteries have been widely used as a power supply for driving electric vehicles (EVs) and hybrid electric vehicles (HEVs and PHEVs), and in stationary storage battery systems for suppressing output fluctuation of solar power generation and wind power generation, for example, and for a peak shift of system power that utilizes the power during the daytime while saving the power during the nighttime.[0003]The use of EVs,...

AI Technical Summary

Benefits of technology

The invention relates to a nonaqueous electrolyte secondary battery with improved cycling characteristics. The battery uses a lithium salt with the oxalate complex as an anion, which helps to prevent decomposition of the electrolyte and form a protective covering on the interface of the electrodes. The electrodes have a rib structure to improve their stability and performance. The battery also contains LiPF2O2 as an additive, which further enhances the protective covering and prevents direct reaction between the electrodes and the solvent, resulting in a battery with excellent charge storage characteristics.

Problems solved by technology

A problem has been found in that a reaction inside an electrode is likely to occur in a non-uniform manner in a winding electrode assembly including a positive electrode with a large width and a negative electrode with a large width.

However, when the reaction inside the electrode occurs in a non-uniform manner, a protective covering derived from the lithium salt having the oxalate complex as an anion is less likely to be formed uniformly on the surface of the negative electrode, and the cycling characteristics are less likely to be improved.

However, a large additive amount of the lithium salt having the oxalate complex as an anion in the nonaqueous electrolyte increases the viscosity of the nonaqueous electrolyte.

In addition, high heat is generated when the positive electrode collector or the negative electrode collector is welded to the positive electrode substrate exposed portion or the negative electrode substrate exposed portion.

Images